Brenner Base Tunnel: Experiences of the main tunnel tubes with single‐shield TBMs in lot H41 Sill Gorge – Pfons

Abstract The construction lot H41 Sill Gorge – Pfons is one of the largest construction lots of the Brenner base tunnel, continuing the construction work in Austria from the Sill Gorge to Pfons, based on the previous construction lots. The findings from the approximately 16.6 km long exploratory tunnel, which was driven with an open gripper TBM in combination with anchors and shotcrete ground support measures, were taken into account in planning the mechanized excavation of the main tunnel tubes, each just over 8 km long, with single‐shield TBMs. Meanwhile, the mechanized tunnelling of the main tunnel tubes using a single‐shield TBM in combination with a predominantly single‐shell sealed segmental lining are very advanced and will reach the lot boundary with the neighbouring construction lot H53 Pfons ‐ Brenner in summer 2025. During the mechanized tunnelling, several fault zones have been driven through that had already been excavated with the exploratory tunnel. This paper presents the experience gained to date from the mechanized excavation of the main tunnel tubes with single‐shield TBMs, as a comparison to the findings from the mechanized excavation of the exploratory tunnel with an open gripper TBM, based on different boundary conditions.